The present invention relates to tools for dispersing various substances in a liquid. More particularly, the present invention relates to a tool that is powered by an air motor and that is adapted to disperse biological samples in relatively small liquid batches and to blend or homogenize the sample.
In order to produce certain types of biochemical Products, it is known to create a fermentation broth in which microorganisms are reproduced. These growing microorganisms create various fermentation products in a known manner. Many of the desired fermentation products created by the growing of microorganisms in a fermentation broth are contained either within the cell wall of the individual microorganism, or are attached to the cell wall of the microorganism. In order to recover these products, it is normally desirable to expose the individual microorganisms to an appropriate solution or solvent.
The exposure of the cells is generally accomplished by homogenizing the mixture of cells with a dispersion tool. An appropriate solvent can be added to the liquid dispersion to aid in extracting the desired fermentation product or compound. The solvent is generally selected depending upon the solubility of the product or compound of interest, such that the desired product or compound can be uniformly dispersed in suspension. The selection of the appropriate solvent is known by those skilled in the art, and will not be discussed further here.
Conventional dispersion tools for homogenizing such a cell dispersion are generally driven by electric motors. These motors are generally very bulky, at least for the horsepower generated, and generally create a considerable amount of heat due to friction.
One problem with the conventional dispersion tools is that, because the drive motors create a considerable amount of heat, the heat is transmitted through the dispersion tool to the cell dispersion. Because many types of biological products and compounds are extremely temperature sensitive, this excess heat has the potential for destroying many of the desired compounds and products. In addition, the excess heat reduces the life expectancy of both the dispersion tool and the motor.
Another problem with the conventional dispersion tools is that the drive motors frequently create sparks. This creates the potential to ignite the solvent in the cell dispersion where flamible solvents are employed.
According to the present invention, a device for homogenizing a liquid containing a plurality of suspended particles is provided. The device includes a shroud for channeling the liquid and suspended particles. The shroud defines an inner bore that is formed to include an axial inlet opening and at least one spaced apart outlet opening. A dispersion bit is provided that is disposed within the inner bore for manipulating the liquid and suspended particles to form a homogenized substance. The bit includes a shear blade attached to the bit at a location near the inlet opening, with the shear blade configured to cooperate with shear outlet openings to shear a portion of the suspended particles. The bit also includes a spiral portion that is configured to draw the liquid and suspended particles axially into and through the inner bore from the inlet opening.
One feature of the foregoing structure is that the bit is configured to include both a shear blade and a spiral portion. One advantage of this feature is that the shear blade acts to shear a portion of the suspended particles in the liquid. In addition, the spiral portion acts to create an upward pumping motion for the liquid and suspended particles which assures recycling of heavier particulate material through the dispersion tool.
In preferred embodiments of the present invention, the inner bore is divided into a first chamber and a separate second chamber. In addition, the bit is configured to include an outwardly extending flange that cooperates with a chamfer on the inner bore to sealingly separate the first chamber from the second chamber. One advantage of this feature is that the liquid to be homogenized is not permitted to enter the second chamber. This is advantageous because the second chamber of the inner bore is configured to accommodate the attachment end of the air motor, which is ideally isolated from any of the liquid to be homogenized.
Also in preferred embodiments of the present invention, the shroud is configured to include additional secondary outlet openings spaced apart from the primary outlet openings. One advantage of this feature is that, by providing both primary and secondary outlet openings for the shroud, and specifically from the first chamber, the liquid and suspended particles that are being pumped into the first chamber are permitted to escape through the two sets of outlet openings to provide for complete circulation of the liquid and suspended particles.
Also in preferred embodiments of the present invention, the shroud is configured to include vent outlets to permit venting of the second chamber. One advantage of this feature is that by providing vent outlets from the second chamber, it is possible to introduce air into the second chamber which exits through the vent openings. This enables the second chamber to be pressurized slightly, which aids in preventing any of the liquid or suspended particles from entering the second chamber.
Thus, the dispersion device of the present invention provides for improved homogenization of a fermentation product without introducing any significant heat into the suspension. The tool is driven by an air motor, which permits unattended operation of the tool without the chance of solvent fires. The tool is capable of performing the dispersion operation more efficiently and in a shorter period of time than was heretofore possible.
Additional objects, features, and advantages of the invention will be apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.